Cathode-ray tube screening correction lens with a non-solarizing material

ABSTRACT

Essentially, the device comprises a rigid transparent substrate, such as glass, and a nonsolarizing polymer layer, such as silicone resin, on the substrate. An effective surface is formed on the surface of the polymer layer opposite the substrate.

United States Patent DAmato July 8, 1975 [54] CATHODE-RAY TUBE SCREENING3,486,825 12/1969 Howland 350/175 NG CORRECTION LENS WITH ANON'SOLARIHNG MATERIAL Primary Examiner-Ronald L. Wibert [75] Inventor:Ralph .lames DAmato, Lancaster, Assistant ExaminerConrad Clark Pa.Attorney, Agent, or Firm-Glenn H. Bruestle; Dennis [73] Assignee: RCACorporation, New York, NY. lrlbeck [22] Filed: May 2, 1973 [211 App].No.: 356,454 [57] ABSTRACT [52] U S Cl 350/189. 350/175 NG Essentially,the device comprises a rigid transparent [51] 1 l3/l8. Gozb 3/04substrate, such as glass, and a nonsolarizing polymer [58} Fieid 350/189175 N6 layer, such as silicone resin, on the substrate. An effectivesurface is formed on the surface of the polymer Reierences Cited layeropposite the substrate.

UNITED STATES PATENTS 9 Claims, 6 Drawing Figures 3,279,340 [Ci/I966Ramberg et al. 350/l89 CATI-IODE-RAY TUBE SCREENING CORRECTION LENS WITHA NON-SOLARIZING MATERIAL BACKGROUND OF THE INVENTION This inventionrelates to refractive devices such as optical correcting lenses for usein laying down arrays of color phosphor deposits in cathode-ray tubes.

Many cathode-ray tubes have mosaic screens or targets of different lightemitting or absorbing material. For example, certain types of colortelevision picture tubes usually include a screen comprising arrays ofred, green, and blue emitting phosphor lines or dots, electron gun meansfor exciting the screen, and a color selection electrode e.g., anapertured sheet metal mask or a wire grill, interposed between the gunmeans and the screen. In one prior art process for forming each colorarray of phosphor lines or dots on a viewing faceplate within a tubehaving an apertured mask, the inner surface of the faceplate is coatedwith a mixture of phosphor particles adapted to emit light of one of thethree colors (e.g., green). and a photosensitive binder. Light isprojected from a source through the apertured mask and onto the coatingso that the apertured mask functions as a photographic master. Theexposed coating is subsequently developed to produce phosphor elementsof the first phosphor, e.g., green emitting lines or dots. The processis repeated for the blue-emitting phosphor and red-emitting phosphorutilizing the same apertured mask but repositioning the source of lightfor each exposure. A more complete description of a prior art processfor forming a picture tube screen can be found in U.S. Pat. No.2,625,734 issued to Law on Jan. 20, 1953.

In exposing the screen through the mask apertures, the light source issequentially placed in a fixed relationship with each center ofdeflection of each of the electron beams which later will excite thescreen. Unfortunately. these deflection centers are not similarly fixedin position but rather vary in position during operation of the tube.One such variation is a shift toward the screen as the angle ofdeflection increases. This shift of the deflection center parallel tothe tube axis causes a radial misregister of the electron impingementspots on the screen with respect to their corresponding phosphor dotsestablished using a fixed light source.

In the case of a dot screen where three beams are subjected to dynamicconvergence, an additional type of deflection center shift occurs. Thisadditional shift is transverse ,to the tube axis and causes degrouping(e.g., an increase in size of the electron spot trios) misregister ofthe electron spots related to their associated phosphor dots. These andother types of misregister are dis cussed in greater detail in thefollowing US. patents: 2,885,935 Epstein et al. and 3,282,691 Morrell etal.

In order to correct error between the position of electron beam landingand the location of a phosphor dot, the prior art has providedcorrecting lenses located between the light source and the tube screenwhich pro vide appropriate deflection of the light rays so as to locatethe position of the phosphor dots at the expected landing positions onthe screen of the electron beams. The design of correcting lenses foruse in fabricating color television picture tubes has been described byEpstein et al in U.S. Pat. Nos. 2,817,276 and 2,885,935, by Ramberg inUS. Pat. No. 3,279,340 and more recently by Yamazaki et al. in US. Pat.No.

LII

3,628,850. The lenses disclosed in the latter two patents havediscontinuous surfaces that permit more accurate exposure of the screen.It becomes more difficult to form a lens out of glass as the complexityof the discontinuous surface increases. Therefore, multielement lenses,such as those shown in US. Pat. No. 3,628,850, are preferablyconstructed of plastics. Unfortunately, the use of most plastic lensesin color picture tube screening lighthouses has several disadvantages.Probably the greatest disadvantage is that all plastic lenses in presentuse decrease in ultraviolet transmission or solarize with exposure toultraviolet radiation in the 290 to 400 namometer range, hereinafterreferred to as the near range. Because of this darkenin or solarization,plastic lenses have to be replaced at frequent intervals. Anotherdisadvantage of plastic lenses is that if they are made too thin, theywill lack adequate mechanical stability.

Each of the disadvantages of the prior art use of plastic lenses isovercome by the present invention. Additionally, the present inventionprovides a less expensive lens than lenses constructed completely out ofglass.

SUMMARY OF THE INVENTION The present invention provides a refractivedevice such as for use in the formation of a color picture tube screen.At least a portion of the device has an effective surface thereon forchanging paths of light rays passing through the device lens. Theportion is constructed of a polymer that is substantially nonsolarizingwhen exposed to ultraviolet radiation in the 290 to 400 nanometer range.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of acorrecting lens embodying the present invention.

FIG. 2 is a perspective view of a second correcting lens embodying thepresent invention.

FIG. 3 is a cross-sectional view of a lens package in corporating thelens of FIG. 2.

FIG. 4 is a cross-sectional view of a second lens package incorporatingthe lens of FIG. 2.

FIG. 5 is a cross-sectional view of a third lens package incorporatingthe lens of FIG. 2.

FIG. 6 is a cross-sectional view of a fourth lens package incorporatingthe lens of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates arefracting device or correcting lens 10 formed with a rigid transparentsubstrate 12. A thinner transparent nonsolarizing polymer layer 14 isuniformly attached to the substrate 12. A surface 16 of the layer 14,opposite the substrate 12, is the effective surface of the lens 10. Thesurface 16 is contoured to provide correction of the light path to thedifferent areas of the screen to prevent misregister.

In a preferred embodiment, the substrate 12 is /4 inch thick opticalglass of suitable quality, such as a glass manufactured by Schott Glass,Inc. designated 8K7. The transparent polymer layer 14 may be any polymerthat has good ultraviolet transmission characteristics, resistssolarization in the wavelength range of 290 to 400 nanometers andexhibits low shrinkage. A material that meets these criteria, and hasbeen found to be preferable is transparent silicone resin. One siliconeresin that has been found suitable for layer 14 is manufactured byDow-Corning. Inc., and is designated R63- 489. The silicone resin layercan be any reasonable thickness, as long as it is thick enough toaccomodate the irregularities of the effective surface. A thickness of Imils has been found to be satisfactory for the lens of FIG. I.

The lens 10 can be formed by any suitable construction technique. In apreferred method. a primer, such as manufactured by Dow-Corning anddesignated Sylgard, is first applied to the glass substrate 12. Then liquid silicone resin, such as R63-489 is mixed with a hardener, such asthat provided by Dow-Corning with the R63-4 89, and is injected into amold between a die contoured with a reverse effective surface shape andthe glass substrate. After the silicone resin has hardened, one side ofit adheres to the primed glass substrate while the other side containsthe effective surface. Although a primer has been used in this preferredmethod to ensure adhesion of the silicone resin to the substrate.adequate adhesion may be attained without use of the primer.

FIG. 2 depicts a second correcting lens 18 also formed with a rigidtransparent substrate 20 and a thin transparent polymer layer 22. Theeffective surface 24 of this lens I8 is divided into a plurality ofsegments 26 each of which provide individualized optical correction forcorresponding parts of the tube screen during screen formation by knownphotoprinting methods. The preferred materials and dimensions used toconstruct lens 18 are the same as those described with respect to lensI0 except that a thickness of 30 to mils is sufficient for the polymerlayer since the variations from the mean surface level seldom exceed l0mils.

Discontinuous interfaces 28 are located between each of the segments 26of the lens 18. A portion of the light passing through the lens 18 mayreflect and scatter therefrom. Therefore, it may be desirable to maskthese as described in a copending application entitled Color TelevisionPicture Tube Screening Method" by van Hekken now U.S. Pat. No.3,782,253. Four masking techniques are shown in FIGS. 3, 4, 5 and 6. Ina lens package 30, shown in FIG. 3, the lens 18 is covered with a secondrigid transparent substrate 32 having an opaque pattern 34,corresponding to the discontinuity pattern, thereon. The secondsubstrate 32 is separated from the effective surface of lens 18 by anair gap 36.

A second lens package 38 is shown in FIG. 4. In this package 38, anopaque material 40 is coated directly onto the effective surface of lens18 at the locations of the surface discontinuities 28.

FIG. 5 shows a third lens package 42 wherein the masking pattern is agrid or grill 44 embedded in the polymer material of the layer 22.

In a fourth lens package 46, shown in FIG. 6, an opaque pattern iscoated directly onto the substrate 20 before the polymer layer isapplied. A preferred opaque material for the lens packages 30, 38 and 46is graphite.

All of the foregoing device embodiments have included a rigid substrateand polymer layer. Such construction takes advantage of the fact thatrelatively inexpensive materials that are dimensionally stable andreadily finished to desired optical requirements, such as glasses, canbe used to support thinlayers of a relatively expensive nonsolarizingpolymer. Therefore, the overall cost of a lens so constructed can besignificantly less than a lens constructed entirely of the nonsolarizinglens material. i

It should be recognized that heretofore no plastic or polymer lens forscreening of color television picture tube screens has ever beenconstructed that is substantially nonsolarizing when exposed toultraviolet radiation in the 290 to 400 nanometer range. The presentinvention provides the art with nonglass lenses that will not solarizeto the extent that they require frequent replacement. Therefore, thepresent invention can significantly reduce the cost of producing colortelevision picture tubes.

Although the term lens has been used in describing the prior art and thepreferred embodiments, it is to be understood that such term has been inlong use in the television screening art to describe refractive devicesthat change or correct paths of light rays but do not provide focusing.It also should be noted that for various reasons known in the art, lightray path correction may not be made to exactly correspond to the path anelectron beam will take in striking the screen. For ex ample, in acompromise to compensate for mask doming caused by heat expansion, itmay be desirable to provide slight misregister. Therefore, thecorrection lens may provide light path corrections to parts of thescreen to substantially, but not exactly, correspond them to the pathselectron beams will take.

I claim:

1. A refractive device for correcting the paths oflight rays in theformation of a color television picture tube screen comprising,

at least a portion of said device having an effective surface thereonfor correcting paths of light rays passing therethrough during formationof said screen to substantially correspond to paths electron beams willtake in striking the screen in a completed tube, said portion being asilicone resin that is substantially nonsolarizing when exposed toultraviolet radiation in the range of 290 to 400 nanometers, and

a rigid transparent substrate for supporting said portion.

2. The device as defined in claim 1, wherein said effective surface is acontinuously contoured surface.

3. The device as defined in claim 1, wherein said effective surface hasat least one surface discontinuity.

4. The device as defined in claim 3, including a mask grid embedded insaid portion and aligned with said discontinuity.

5. The device as defined in claim I, wherein said effective surface hasat least one surface discontinuity and said substrate includes a maskpattern on a surface thereof, said mask pattern aligned with saiddiscontinuity.

6. A refractive device for correcting the paths of light rays in theformation of a color television picture tube screen comprising,

a rigid transparent substrate,

a transparent silicone resin layer uniformly attached to said substrate,said silicone resin being a material having good ultraviolettransmission characteristics and being resistant to solarization in theultraviolet wavelength range of 290 to 400 nanometers of colortelevision picture tube screening devices, said silicone resin layerhaving an effective surface thereon for correcting paths of light rayspassing therethrough during formation of said screen to 6 substantiallycorrespond to paths electron beams 8. The device as defined in claim 6,wherein thickwill take in striking the screen in a completed tube. messf said polymer layer is less than o mils 7. The device as defined inclaim 6, wherein the sili- The device as defined in Claim 8 whgreinthick cone resin has ultraviolet transmission characteristics andsolarization resistance similar to a silicone resin manufactured byDowwCorning, Inc. and designated R63-489.

ness of said polymer layer is within the range of 30 to 40 mils.

1. A refractive device for correcting the paths of light rays in theformation of a color television picture tube screen comprising, at leasta portion of said device having an effective surface thereon forcorrecting paths of light rays passing therethrough during formation ofsaid screen to substantially correspond to paths electron beams willtake in striking the screen in a completed tube, said portion being asilicone resin that is substantially nonsolarizing when exposed toultraviolet radiation in the range of 290 to 400 nanometers, and a rigidtransparent substrate for supporting said portion.
 2. The device asdefined in claim 1, wherein said effective surface is a continuouslycontoured surface.
 3. The device as defined in claim 1, wherein saideffective surface has at least one surface discontinuity.
 4. The deviceas defined in claim 3, including a mask grid embedded in said portionand aligned with said discontinuity.
 5. The device as defined in claim1, wherein said effective surface has at least one surface discontinuityand said substrate includes a mask pattern on a surface thereof, saidmask pattern aligned with said discontinuity.
 6. A refractive device forcorrecting the paths of light rays in the formation of a colortelevision picture tube screen comprising, a rigid transparentsubstrate, a transparent silicone resin layer uniformly attached to saidsubstrate, said silicone resin being a material having good ultraviolettransmission characteristics and being resistant to solarization in theultraviolet wavelength range of 290 to 400 nanometers of colortelevision picture tube screening devices, said silicone resin layerhaving an effective surface thereon for correcting paths of light rayspassing therethrough during formation of said screen to substantiallycorrespond to paths electron beams will take in striking the screen in acompleted tube.
 7. The device as defined in claim 6, wherein thesilicone resin has ultraviolet transmission characteristics andsolarization resistance similar to a silicone resin manufactured byDow-Corning, Inc. and designated R63-489,
 8. The device as defined inclaim 6, wherein thickness of said polymer layer is less than 100 mils.9. The device as defined in claim 8, wherein thickness of said polymerlayer is within the range of 30 to 40 mils.